1. Technical Field
The present invention relates to a gas cell unit and an atomic oscillator.
2. Related Art
An atomic oscillator oscillating based on an energy transition in an alkali metal atom such as rubidium or cesium is generally classified into an atomic oscillator using a double resonance phenomenon of light and microwave (see, for example, JP-A-10-284772) and an atomic oscillator using a quantum interference effect (CPT: Coherent Population Trapping) of two kinds of lights different in wavelength (see, for example, U.S. Pat. No. 6,806,784).
In both the atomic oscillators, in general, the alkali metal, together with buffer gas, is sealed in a gas cell, and the gas cell is required to be heated to a specific temperature in order to keep the alkali metal in a gaseous state.
For example, in an atomic oscillator disclosed in US Patent Publication No. 2006/0022761, a film-like heater made of ITO is provided on the outer surface of a gas cell in which a gaseous metal atom is sealed, and the heater is heated by energization. By this, the gas cell is heated, and the metal atom in the gas cell can be kept in the gaseous state.
In the atomic oscillator as stated above, in general, current supplied to the heater is adjusted so that the temperature in the gas cell becomes constant. Thus, the current flowing through the heater is changed according to, for example, the change of outer temperature.
When the current flowing through the heater is changed as stated above, the magnetic field generated from the heater is also changed.
When the magnetic field generated from the heater is changed, a frequency corresponding to an energy difference between the ground levels of the metal atom in the gas cell is changed. Thus, in the related art atomic oscillator, there is a problem that the output frequency shifts.